1. Field of the Invention
The present invention relates to a storage device, and more particularly, to a method for estimating capacity usage status of a storage unit, an associated storage device and an associated controller.
2. Description of the Prior Art
Some external storage devices have screens positioned thereon to show their residual or used capacity. If, however, the residual or used capacity is calculated by a microprocessor of the external storage device, the calculation may require a lot of time because of heavy reading operations. Moreover, because storage capacities of the external storage devices have increased in size, calculating the residual capacity or the used capacity will waste even more time than before, causing inconvenience to the users.
The external storage device also includes a controller and a storage unit, where the controller is used to access the storage unit. Assuming that the controller needs to read data stored in sectors 1 and 2 of the storage unit, a flow of the operations of the controller is described as follows:
Step 1: The controller transmits a position command corresponding to the sector 1 to the storage unit.
Step 2: The controller waits for a response message from the storage unit.
Step 3: After receiving the response message from the storage unit, the controller receives the data stored in sector 1.
Step 4: Steps 1-3 are repeated to receive data stored in the sector 2.
In light of the above, only when the storage unit sends back the response message can the controller receive the data and transmit a next position command to the storage unit. Therefore, how to use this waiting time (Step 2) to enhance the efficiency of the controller is an important topic in this field.